Mercurial > SDL_sound_CoreAudio
annotate decoders/mpglib.c @ 474:c66080364dff
Most decoders now report total sample play time, now. Technically, this
breaks binary compatibility with the 1.0 branch, since it extends the
Sound_Sample struct, but most (all?) programs are just passing pointers
allocated by SDL_sound around, and might be okay.
Source-level compatibility is not broken...yet! :)
--ryan.
-------- Original Message --------
Subject: SDL_sound patch: Finding total length of time of sound file.
Date: Sun, 26 Jan 2003 09:31:17 -0800 (PST)
Hi Ryan,
I am working with Eric Wing and helping him modify
SDL_sound. AS part of our efforts in improving and
enhancing SDL_sound, we like to submit this patch. We
modified the codecs to find the total time of a sound
file. Below is the explanation of the patch. The
patch is appended as an attachment to this email.
* MOTIVATION:
We needed the ability to get the total play time of a
sample (And we noticed that we're not the only ones).
Since SDL_sound blocks direct access to the specific
decoders, there is no way for a user to know this
information short of decoding the whole thing.
Because of this, we believe this will be a useful
addition, even though the accuracy may not be perfect
(subject to each decoder) or the information may not
always be available.
* CONTRIBUTORS:
Wesley Leong (modified the majority of the codecs and
verified the results)
Eric Wing (showed everyone how to do modify codec,
modified mikmod)
Wang Lam (modified a handful of codecs, researched
into specs and int overflow)
Ahilan Anantha (modified a few codecs and helped with
integer math)
* GENERAL ISSUES:
We chose the value to be milliseconds as an Sint32.
Milliseconds because that's what Sound_Seek takes as a
parameter and -1 to allow for instances/codecs where
the value could not be determined. We are
not sure if this is the final convention you want, so
we are willing to work with you on this.
We also expect the total_time field to be set on open
and never again modified by SDL_sound. Users may
access it directly much like the sample buffer and
buffer_size. We thought about recomputing the time
on DecodeAll, but since users may seek or decode small
chunks first, not all the data may be there. So this
is better done by the user. This may be good
information to document.
Currently, all the main codecs are implemented except
for QuickTime.
| author | Ryan C. Gordon <icculus@icculus.org> |
|---|---|
| date | Sat, 08 May 2004 08:19:50 +0000 |
| parents | cbb15ecf423a |
| children | 3e705c9180e5 |
| rev | line source |
|---|---|
| 261 | 1 /* |
| 2 * SDL_sound -- An abstract sound format decoding API. | |
| 3 * Copyright (C) 2001 Ryan C. Gordon. | |
| 4 * | |
| 5 * This library is free software; you can redistribute it and/or | |
| 6 * modify it under the terms of the GNU Lesser General Public | |
| 7 * License as published by the Free Software Foundation; either | |
| 8 * version 2.1 of the License, or (at your option) any later version. | |
| 9 * | |
| 10 * This library is distributed in the hope that it will be useful, | |
| 11 * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 13 * Lesser General Public License for more details. | |
| 14 * | |
| 15 * You should have received a copy of the GNU Lesser General Public | |
| 16 * License along with this library; if not, write to the Free Software | |
| 17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
| 18 */ | |
| 19 | |
| 20 /* | |
| 21 * MPGLIB decoder for SDL_sound. This is a very lightweight MP3 decoder, | |
| 22 * which is included with the SDL_sound source, so that it doesn't rely on | |
| 23 * unnecessary external libraries. | |
| 24 * | |
| 25 * The SMPEG decoder plays back more forms of MPEGs, and may behave better or | |
| 26 * worse under various conditions. mpglib is (apparently) more efficient than | |
| 27 * SMPEG, and, again, doesn't need an external library. You should test both | |
| 28 * decoders and use what you find works best for you. | |
| 29 * | |
|
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30 * mpglib is an LGPL'd portion of mpg123, which can be found in its original |
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31 * form at: http://www.mpg123.de/ |
| 261 | 32 * |
| 33 * Please see the file COPYING in the source's root directory. The included | |
| 34 * source code for mpglib falls under the LGPL, which is the same license as | |
| 35 * SDL_sound (so you can consider it a single work). | |
| 36 * | |
| 37 * This file written by Ryan C. Gordon. (icculus@clutteredmind.org) | |
| 38 */ | |
| 39 | |
| 40 #if HAVE_CONFIG_H | |
| 41 # include <config.h> | |
| 42 #endif | |
| 43 | |
| 44 #ifdef SOUND_SUPPORTS_MPGLIB | |
| 45 | |
| 46 #include <stdio.h> | |
| 47 #include <stdlib.h> | |
| 48 #include <string.h> | |
| 49 #include "mpglib/mpg123_sdlsound.h" | |
| 50 #include "mpglib/mpglib_sdlsound.h" | |
| 51 | |
| 52 #include "SDL_sound.h" | |
| 53 | |
| 54 #define __SDL_SOUND_INTERNAL__ | |
| 55 #include "SDL_sound_internal.h" | |
| 56 | |
| 57 static int MPGLIB_init(void); | |
| 58 static void MPGLIB_quit(void); | |
| 59 static int MPGLIB_open(Sound_Sample *sample, const char *ext); | |
| 60 static void MPGLIB_close(Sound_Sample *sample); | |
| 61 static Uint32 MPGLIB_read(Sound_Sample *sample); | |
| 62 static int MPGLIB_rewind(Sound_Sample *sample); | |
|
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63 static int MPGLIB_seek(Sound_Sample *sample, Uint32 ms); |
| 261 | 64 |
| 65 static const char *extensions_mpglib[] = { "MP3", NULL }; | |
| 66 const Sound_DecoderFunctions __Sound_DecoderFunctions_MPGLIB = | |
| 67 { | |
| 68 { | |
| 69 extensions_mpglib, | |
| 70 "MP3 decoding via internal mpglib", | |
| 71 "Ryan C. Gordon <icculus@clutteredmind.org>", | |
| 72 "http://www.icculus.org/SDL_sound/" | |
| 73 }, | |
| 74 | |
| 75 MPGLIB_init, /* init() method */ | |
| 76 MPGLIB_quit, /* quit() method */ | |
| 77 MPGLIB_open, /* open() method */ | |
| 78 MPGLIB_close, /* close() method */ | |
| 79 MPGLIB_read, /* read() method */ | |
|
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80 MPGLIB_rewind, /* rewind() method */ |
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81 MPGLIB_seek /* seek() method */ |
| 261 | 82 }; |
| 83 | |
| 84 | |
| 85 /* this is what we store in our internal->decoder_private field... */ | |
| 86 typedef struct | |
| 87 { | |
| 88 struct mpstr mp; | |
| 89 Uint8 inbuf[16384]; | |
| 90 Uint8 outbuf[8192]; | |
| 91 int outleft; | |
| 92 int outpos; | |
| 93 } mpglib_t; | |
| 94 | |
| 95 | |
| 96 | |
| 97 static int MPGLIB_init(void) | |
| 98 { | |
| 99 return(1); /* always succeeds. */ | |
| 100 } /* MPGLIB_init */ | |
| 101 | |
| 102 | |
| 103 static void MPGLIB_quit(void) | |
| 104 { | |
| 105 /* it's a no-op. */ | |
| 106 } /* MPGLIB_quit */ | |
| 107 | |
| 108 | |
| 109 static int MPGLIB_open(Sound_Sample *sample, const char *ext) | |
| 110 { | |
| 111 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 112 mpglib_t *mpg = NULL; | |
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113 int rc; |
| 261 | 114 |
| 115 /* | |
| 116 * If I understand things correctly, MP3 files don't really have any | |
| 117 * magic header we can check for. The MP3 player is expected to just | |
| 118 * pick the first thing that looks like a valid frame and start | |
| 119 * playing from there. | |
| 120 * | |
| 121 * So here's what we do: If the caller insists that this is really | |
| 122 * MP3 we'll take his word for it. Otherwise, use the same test as | |
| 123 * SDL_mixer does and check if the stream starts with something that | |
| 124 * looks like a frame. | |
| 125 * | |
| 126 * A frame begins with 11 bits of frame sync (all bits must be set), | |
| 127 * followed by a two-bit MPEG Audio version ID: | |
| 128 * | |
| 129 * 00 - MPEG Version 2.5 (later extension of MPEG 2) | |
| 130 * 01 - reserved | |
| 131 * 10 - MPEG Version 2 (ISO/IEC 13818-3) | |
| 132 * 11 - MPEG Version 1 (ISO/IEC 11172-3) | |
| 133 * | |
| 134 * Apparently we don't handle MPEG Version 2.5. | |
| 135 */ | |
| 136 if (__Sound_strcasecmp(ext, "MP3") != 0) | |
| 137 { | |
| 138 Uint8 mp3_magic[2]; | |
| 139 | |
| 140 if (SDL_RWread(internal->rw, mp3_magic, sizeof (mp3_magic), 1) != 1) | |
|
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141 BAIL_MACRO("MPGLIB: Could not read MP3 magic.", 0); |
| 261 | 142 |
| 143 if (mp3_magic[0] != 0xFF || (mp3_magic[1] & 0xF0) != 0xF0) | |
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144 BAIL_MACRO("MPGLIB: Not an MP3 stream.", 0); |
| 261 | 145 |
| 351 | 146 /* If the seek fails, we'll probably miss a frame, but oh well. */ |
| 261 | 147 SDL_RWseek(internal->rw, -sizeof (mp3_magic), SEEK_CUR); |
| 148 } /* if */ | |
| 149 | |
| 150 mpg = (mpglib_t *) malloc(sizeof (mpglib_t)); | |
| 151 BAIL_IF_MACRO(mpg == NULL, ERR_OUT_OF_MEMORY, 0); | |
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152 memset(mpg, '\0', sizeof (mpglib_t)); |
| 261 | 153 InitMP3(&mpg->mp); |
| 154 | |
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155 rc = SDL_RWread(internal->rw, mpg->inbuf, 1, sizeof (mpg->inbuf)); |
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156 if (rc <= 0) |
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157 { |
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158 free(mpg); |
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159 BAIL_MACRO("MPGLIB: Failed to read any data at all", 0); |
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160 } /* if */ |
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161 |
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162 if (decodeMP3(&mpg->mp, mpg->inbuf, rc, |
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163 mpg->outbuf, sizeof (mpg->outbuf), |
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164 &mpg->outleft) == MP3_ERR) |
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165 { |
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166 free(mpg); |
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167 BAIL_MACRO("MPGLIB: Not an MP3 stream?", 0); |
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168 } /* if */ |
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169 |
| 261 | 170 SNDDBG(("MPGLIB: Accepting data stream.\n")); |
| 171 | |
| 172 internal->decoder_private = mpg; | |
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173 sample->actual.rate = mpglib_freqs[mpg->mp.fr.sampling_frequency]; |
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174 sample->actual.channels = mpg->mp.fr.stereo; |
| 351 | 175 sample->actual.format = AUDIO_S16SYS; |
| 261 | 176 sample->flags = SOUND_SAMPLEFLAG_NONE; |
| 177 | |
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178 { |
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179 /* Finds approximate length of the song. */ |
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180 Uint32 pos, total_byte_size; |
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181 char tag_buffer[4]; |
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182 memset(tag_buffer, '\0', sizeof(tag_buffer)); |
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183 |
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184 /* Get size of file first */ |
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185 pos = SDL_RWtell(internal->rw); |
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186 total_byte_size = SDL_RWseek(internal->rw, -128, SEEK_END); |
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187 if( total_byte_size <= 0 ) { |
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188 BAIL_MACRO("MPGLIB: Not an MP3 stream.", 0); |
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189 } |
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190 if ( SDL_RWread(internal->rw, tag_buffer, 1, 3) != 3) { |
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191 BAIL_MACRO("MPGLIB: Cannot identify TAG section.", 0); |
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192 } |
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193 if ( strncmp(tag_buffer, "TAG", 3) != 0 ) { |
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194 /* ENDING TAG NOT FOUND */ |
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195 total_byte_size = SDL_RWseek(internal->rw,0, SEEK_END); |
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196 } |
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197 if (SDL_RWseek(internal->rw, pos, SEEK_SET) != pos) { |
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198 BAIL_MACRO("MPGLIB: Cannot go back to save spot in file.", 0); |
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199 } |
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200 sample->total_time = total_byte_size / mpg->mp.fr.bitrate * 8.0; |
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201 sample->total_time += (total_byte_size % mpg->mp.fr.bitrate) * 8.0 |
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202 / mpg->mp.fr.bitrate; |
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203 } |
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204 |
| 261 | 205 return(1); /* we'll handle this data. */ |
| 206 } /* MPGLIB_open */ | |
| 207 | |
| 208 | |
| 209 static void MPGLIB_close(Sound_Sample *sample) | |
| 210 { | |
| 211 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 212 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private); | |
| 213 ExitMP3(&mpg->mp); | |
| 214 free(mpg); | |
| 215 } /* MPGLIB_close */ | |
| 216 | |
| 217 | |
| 218 static Uint32 MPGLIB_read(Sound_Sample *sample) | |
| 219 { | |
| 220 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 221 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private); | |
| 222 Uint32 bw = 0; | |
| 223 int rc; | |
| 224 | |
| 225 while (bw < internal->buffer_size) | |
| 226 { | |
| 227 if (mpg->outleft > 0) | |
| 228 { | |
| 229 Uint16 cpysize = internal->buffer_size - bw; | |
| 230 if (cpysize > mpg->outleft) | |
| 231 cpysize = mpg->outleft; | |
| 232 memcpy(((Uint8 *) internal->buffer) + bw, | |
| 233 mpg->outbuf + mpg->outpos, cpysize); | |
| 234 bw += cpysize; | |
| 235 mpg->outpos += cpysize; | |
| 236 mpg->outleft -= cpysize; | |
| 237 continue; | |
| 238 } /* if */ | |
| 239 | |
| 240 /* need to decode more from the MP3 stream... */ | |
| 241 mpg->outpos = 0; | |
| 242 rc = decodeMP3(&mpg->mp, NULL, 0, mpg->outbuf, | |
| 243 sizeof (mpg->outbuf), &mpg->outleft); | |
| 244 if (rc == MP3_ERR) | |
| 245 { | |
| 246 sample->flags |= SOUND_SAMPLEFLAG_ERROR; | |
| 247 return(bw); | |
| 248 } /* if */ | |
| 249 | |
| 250 else if (rc == MP3_NEED_MORE) | |
| 251 { | |
| 252 rc = SDL_RWread(internal->rw, mpg->inbuf, 1, sizeof (mpg->inbuf)); | |
| 253 if (rc == -1) | |
| 254 { | |
| 255 sample->flags |= SOUND_SAMPLEFLAG_ERROR; | |
| 256 return(bw); | |
| 257 } /* if */ | |
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258 |
| 261 | 259 else if (rc == 0) |
| 260 { | |
| 261 sample->flags |= SOUND_SAMPLEFLAG_EOF; | |
| 262 return(bw); | |
| 263 } /* else if */ | |
| 264 | |
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265 /* make sure there isn't an ID3 tag. */ |
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266 /* |
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267 * !!! FIXME: This can fail under the following circumstances: |
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268 * First, if there's the sequence "TAG" 128 bytes from the end |
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269 * of a read that isn't the EOF. This is unlikely. |
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270 * Second, if the TAG sequence is split between two reads (ie, |
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271 * the last byte of a read is 'T', and the next read is the |
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272 * final 127 bytes of the stream, being the rest of the ID3 tag). |
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273 * While this is more likely, it's still not very likely at all. |
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274 * Still, something SHOULD be done about this. |
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275 * ID3v2 tags are more complex, too, not to mention LYRICS tags, |
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276 * etc, which aren't handled, either. Hey, this IS meant to be |
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277 * a lightweight decoder. Use SMPEG if you need an all-purpose |
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278 * decoder. mpglib really assumes you control all your assets. |
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279 */ |
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280 if (rc >= 128) |
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281 { |
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282 Uint8 *ptr = &mpg->inbuf[rc - 128]; |
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283 if ((ptr[0] == 'T') && (ptr[1] == 'A') && (ptr[2] == 'G')) |
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284 rc -= 128; /* disregard it. */ |
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285 } /* if */ |
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286 |
| 263 | 287 rc = decodeMP3(&mpg->mp, mpg->inbuf, rc, |
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288 mpg->outbuf, sizeof (mpg->outbuf), |
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289 &mpg->outleft); |
| 261 | 290 if (rc == MP3_ERR) |
| 291 { | |
| 292 sample->flags |= SOUND_SAMPLEFLAG_ERROR; | |
| 293 return(bw); | |
| 294 } /* if */ | |
| 295 } /* else if */ | |
| 296 } /* while */ | |
| 297 | |
| 298 return(bw); | |
| 299 } /* MPGLIB_read */ | |
| 300 | |
| 301 | |
| 302 static int MPGLIB_rewind(Sound_Sample *sample) | |
| 303 { | |
| 304 Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque; | |
| 305 mpglib_t *mpg = ((mpglib_t *) internal->decoder_private); | |
| 306 BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0); | |
| 307 | |
| 308 /* this is just resetting some fields in a structure; it's very fast. */ | |
| 309 ExitMP3(&mpg->mp); | |
| 310 InitMP3(&mpg->mp); | |
| 311 mpg->outpos = mpg->outleft = 0; | |
| 312 return(1); | |
| 313 } /* MPGLIB_rewind */ | |
| 314 | |
| 315 | |
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316 static int MPGLIB_seek(Sound_Sample *sample, Uint32 ms) |
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317 { |
| 351 | 318 BAIL_MACRO("MPGLIB: Seeking not implemented", 0); |
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319 } /* MPGLIB_seek */ |
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320 |
| 261 | 321 #endif /* SOUND_SUPPORTS_MPGLIB */ |
| 322 | |
| 323 | |
| 324 /* end of mpglib.c ... */ | |
| 325 |